Information handling systems often utilize multiple voltage regulators to provide power to various sub-systems. In order to replenish the high-frequency current delivered by small value decoupling capacitors at the load, a voltage regulator often employs a bulk capacitor at its output to store charge and supply outrush current from the stored charge to the decoupling capacitors in response to an increase in the current load for the purpose of reducing voltage droop at the output of the voltage regulator. The presence of this bulk capacitor at the output of the voltage regulator is a significant inhibitor of a rapid ramp-up of the output voltage to a target voltage due to the inrush current to the bulk capacitor at start-up for the purpose of charging the bulk capacitor. As different voltage regulators in an information handling system may have different performance characteristics, including different output voltages and bulk capacitances at their outputs, the voltage ramp-up rates of the voltage regulators in an information handling system can vary significantly. In many instances, those components of the information handling system that utilize power from two or more voltage regulators can be damaged if the supplied voltages are not ramped to their corresponding target voltages at equivalent rates during start-up. Typically, a disparity between the rate at which one voltage ramps up and the rate at which another voltage ramps up can result in reverse biasing of one or more devices of a multiple-voltage component. This reverse bias condition can permanently damage the devices depending on the difference between the voltages and its duration.
One conventional technique to prevent reverse biasing due to disparities between voltage regulator ramp-up rates is to sequence the voltage regulators such that each voltage regulator ramps up its output voltage in turn. This conventional technique often is disadvantageous due to the relatively long start-up time resulting from the accumulation of ramp-up times. Further, additional sequencing control circuitry is required to affect the sequencing, thereby increasing the complexity, power consumption, and cost of the information handling system. Another conventional technique to prevent reverse biasing includes synchronizing the voltage regulators such that each of their outputs are connected to a common voltage rail during their voltage ramp-up and then releasing each voltage regulator's connection to the common voltage rail after the target voltage for the voltage regulator has been reached. This conventional technique typically requires costly pass elements to connect the voltage regulators to the common voltage rail, thereby increasing the complexity and cost of the system. Further, this conventional technique requires substantial time for voltage ramp-up so as to allow the bulk capacitors to charge up. Accordingly, an improved technique for voltage ramp-up of a voltage regulator would be advantageous.
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